These researches are directed at finding a practical method for identifying infants and young children who are at risk of developing amblyopia due either to uncorrected refractive errors or subtle motor problems. They are also aimed at finding the physiological basis of an effective preventative therapy for refractive amblyopia and severe ametropia by investigating emmetropizing mechanisms in humans and animals. To accomplish these goals, we propose to conduct both human and animal studies on refractive development. The results of researches of the past grant period have caused us to focus on the possible interaction of focusing and motor problems in the genesis of amblyopia. In our human studies, we will continue to collect medical history, photo-refractive, visual acuity, accommodative, and convergence data on infants and children from a volunteer laboratory population. In addition, we will collect comparable data from a country-wide school screening population in order to assess selective biases in our laboratory study. We will use this information to construct a practical method for the prediction and, hopefully, prevention of amblyopia on the basis of refractive and motor behavior measured in infanCy. In our animal studies, we will study the growth of the eyes of chicks, using monochromatic light and cylindrical lenses to study their effect on emmetropizing mechanisms. We will also investigate the mechanics of accommodation in chickens, looking at the mechanical and refractive behavior of excised eyes and the mechanical properties of strips of cornea.